Immediate post-operative rehabilitation of the knee or hip joint is desirable following many surgical procedures, including total joint replacement or joint reconstruction, to restore the joint to its full range of motion. Effective rehabilitation requires controlled movement of the knee or hip joint as soon as possible after surgery without bearing weight on the joint or placing a substantial force load on the joint. As rehabilitation progresses, the range of joint movement can be increased and force loads can be applied to the joint.
One type of device that has been developed for rehabilitative leg exercise is termed a continuous passive motion device. Such devices, as for example disclosed in U.S. Pat. No. 4,974,830 to Genovese et al., mount the leg on a rigid support structure while the knee is driven through alternating flexion and extension motion by applying an external force to the knee across a mechanical pivot point. Continuous passive motion devices known in the art, however, require careful anatomical alignment of the rigid support structure with the leg and strict monitoring of the external force loads applied to the leg joints to prevent post-operative injury to the joint during rehabilitation thereof. Furthermore, such devices are relatively complex and cumbersome to operate and maintain, as well as costly to produce.
As such, it is an object of the present invention to provide a device for rehabilitation of a leg joint, and in particular a knee or hip joint, which is portable, relatively inexpensive to produce, and relatively simple to operate and maintain. It is another object of the present invention to provide a device for rehabilitation of the knee or hip joint which is readily adaptable to different size legs without requiring careful anatomical alignment of the device with the knee joint.
It is a further object of the present invention to provide a device that can passively apply a limited external force to the knee or hip joint for range of motion exercise thereof with a minimal risk of injury to the joint. It is another object of the present invention to provide a device that can actively apply a desired degree of the patient's own leg muscle force to the knee or hip joint for range of motion exercise of the joint without bearing weight thereon. It is yet another object of the present invention to provide a device that can be adapted to enable passive suspension of the leg for continuous extension exercise of the knee joint.